Brucella is a genus of pathogenic bacteria which cause acute or chronic illness in many animal species, including humans and cattle. Six species of Brucella and multiple biovars have been characterized by phenotypic methods, although such methods are not always reliable. The six species and multiple biovars of Brucella may also be characterized by their natural host and a strain's geographical origin (See Table 1), however, a species may infect an animal other than its natural host, and a single strain may now be found in multiple geographic locations.
Early detection and characterization of the species or biovar of the infecting Brucella organism would be of great value in medical and veterinary practice. Rapid and reliable detection of Brucella infection is important to permit removal of infected cattle from a healthy herd and prevent the spread of the disease. Characterization of the species or biovar of Brucella would provide epidemiological data to determine the source of the infection.
TABLE 1 ______________________________________ SPECIES BIOVAR STRAIN HOST ORIGIN ______________________________________ B. abortus 1 19 U.S. 1 2308 cattle U.S. 1 RB51 d.2308.sup.a U.S. 1 45/20 d.45/0 England 2 ATCC 23449 cattle/ England 3 ATCC 23450 bison Uganda 4 ATCC 23451 " England 5 ATCC 23452 " England 6 ATCC 23453 " Africa 7 ATCC 23454 " 9 ATCC 23455 " England B. melitensis 1 ATCC 23456 goat U.S. B. suis 1 ATCC 23444 pig U.S. B. neotomae ATCC 23459 desert U.S. wood rat B. canis ATCC 23365 dog U.S. B. ovis ATCC 25840 sheep Africa ______________________________________ ATCC American Type Culture Collection, Bethesda, Maryland. d. derivative
Heretofore, standard serological tests used to detect Brucella have required several weeks time to complete and have not been able to distinguish between species of Brucella. The methods currently available to identify species of infecting Brucella require the isolation of bacteria on selective media followed by quantitative analysis of phenotypic properties of the organism. Phenotypic characterization may be based on such features as lipopolysaccharide antigens, phage typing, dye sensitivities, CO.sub.2 requirements, H.sub.2 S production, and metabolic properties. Such methods are time consuming (requiring 1-4 weeks) and are unreliable. (see Alton, 1988, Techniques for the Brucellosis Laboratory; Moriera-Jacob, 1963, Nature 197:406; Shibata, 1962, Nat. Inst. Anim. Health Q. 2:10-14) Time delays in obtaining test results and uncertainty due to unreliable test results can result in great economic losses. Suspect animals may require quarantine or may contaminate healthy animals in the herd during the waiting period.
Identification of Brucella species using DNA probes has not previously been possible, due to the high degree of inter-species DNA homology (approximately 90%).
There remains a great need for a rapid and accurate method for detecting the presence of pathogenic Brucella organisms in a suspect animal. It is also greatly desirable that such a detection method have the ability to distinguish between and identify the species and/or biovars of Brucella.